Okay so, once you're happy with the starting position you can begin the battle, the camera pans out and shows the 3D battle playing out in real-time. You can cycle through the units (squads, not individual) and use the directional buttons to issue a few orders, as well as being able to zoom in and out the action. The orders in the preview code were fairly limited during battles, you could rally troops, which boosts morale, issue orders to charge and move the squads with the thumb-stick, but the majority of the planning takes place before the game begins. This does mean that you spend the majority of the early battles just sitting back and watching the action unfold, but as you progress you'll need to use these commands to rally your troops and judge when to send one of your individual squads 'charging' at the enemy. The AI is not quite up to scratch as yet, although we understand this preview code is a few months old, and at the moment the squads occasionally override your decisions, which can be frustrating; hopefully this will be ironed out before the game arrives in May.
The PS2 graphics do look dated and fairly blocky, but there are some epic battles with hundreds of troops on screen at any one time and I experienced no issues with frame-rates.
The History Channel : Great Battles of Rome is due for release in May on PC, PS2 and PSP.